The present invention relates generally to semiconductor device structures and, more particularly, to an indirectly induced tunnel emitter for tunnel field effect transistor (TFET) devices.
Microelectronic devices are typically fabricated on semiconductor substrates as integrated circuits, which include complementary metal oxide semiconductor (CMOS) field effect transistors as one of the core elements thereof Over the years, the dimensions and operating voltages of CMOS transistors are continuously reduced, or scaled down, to obtain ever-higher performance and packaging density of the integrated circuits.
However, one of the problems resulting from the scaling down of CMOS transistors is that the overall power consumption of the devices keeps increasing. This is partly because leakage currents are increasing (e.g., due to short channel effects) and also because it becomes difficult to continue to decrease the supply voltage. The latter problem, in turn, is mainly due to the fact that the inverse subthreshold slope is limited to (minimally) about 60 millivolts (mV)/decade, such that switching the transistor from the OFF to the ON states requires a certain voltage variation, and therefore a minimum supply voltage.
Accordingly, tunnel field effect transistors (TFETs) have been touted as “successors” of metal oxide semiconductor field effect transistors (MOSFETs), because of the lack of short-channel effects and because the subthreshold slope can be less than 60 mV/decade, the physical limit of conventional MOSFETs, and thus potentially lower supply voltages may be used. On the other hand, TFETs typically suffer from low on-currents, which is a drawback related to the large resistance of the tunnel barrier.